DESTRUCTIVE DISTILLATION OF MANILA COPAL.- 213 



EXPERIMENTAL. 



Tlie following experiment shows that copal oil is, as a matter of fact, 

 formed by the decomposition of Manila copal at the common working 

 temperature, about 300°. 



About 250 grams of resin were heated to 310° and a reduced pressure of 120 

 millimeters applied. Even witli this slight vacuum 25 grams of a viscous, light 

 yellow oil were obtained. After this amount of oil had been distilled, the heating 

 was continued at ordinary pressure for four hours at 300° to 310°. When 

 reduced pressure was applied, as before, 28 grams of oil were obtained below a 

 temperature of 290°. 



A sample of Manila copal was heated until it had lost about 20 per cent of 

 its weight. A portion of the fused residue was reheated to 200° and an equal 

 quantity of hot, boiled linseed oil added to it. When a' drop of the mixture was let 

 fall on a piece of glass and allowed to cool it remained clear, but after adding more 

 linseed oil, amounting to about 25 per cent of the original quantity of oil, the 

 drop then taken became cloudy on cooling, owing to partial separation of the 

 resin. On adding still more hot boiled linseed oil the resin was precipitated in a 

 bulky sticky mass. 



It will be seen from the above experiment, which was duplicated on 

 many different melted samples, that the behavior of linseed oil as a 

 solvent for heated copals is the same as that of ligroin, turpentine, and 

 benzene. Varnish-like solutions can also be' made of melted resin in 

 coconut oil and heavy mineral oil which boils above 300°. The resulting 

 solutions resemble varnish in their transparency, but of course do not dry. 



The resin was melted exactly as in the preparation of a linseed-oil varnish 

 and heated at 300° until it had lost about 25 per cent of its weight. The hot 

 mineral or coconut oil was then added in the proportions required for a 10-gallon 

 varnish and the heating was continued at about 290° for one-half hour. The 

 drops then tested remained quite clear on cooling. A portion of each solution 

 was thinned with an amount of turpentine equal to the quantity of oil taken. 

 The addition of more mineral or coconut oil to the undiluted portions caused 

 partial precipitation of the resin. 



It is naturally to be expected that the loss of carbon dioxide and 

 water which occurs on fusing the resin will affect its solubility. The 

 melted resin is somewhat richer in hydrocarbons and poorer in acids 

 than the original material. ' The Koettstorfer numbers of melted copals 

 are always lower than those of the natural Resins. The decrease in the 

 Koettstorfer number depends upon the duration and temperature of, 

 and probably the pressure exerted upon the fusion. However, it does 

 not seem to me at all probable that the loss of relatively little carbon 

 dioxide, water, and small quantities of other substances 3T would, in itself, 

 affect the solubility of the copal to any considerable extent. 



37 See page 210. 



